Merck & Co. has done some dramatic things in antibiotics lately. Six months ago, it bought Lexington, Mass.-based Cubist Pharmaceuticals, a leader in the field, for $8.4 billion. Then it laid off a ton of people there. Now it’s joining a $30 million investment in a little company with new ideas for fighting some of the “superbugs.”

Cambridge, Mass.-based Spero, a company founded in 2013 and that previously raised $3 million, is announcing today it has secured a $30 million Series A venture financing. The deal was led by Lundbeckfond Ventures, and included new investors Merck Research Ventures and The Kraft Group (led by Robert Kraft, the owner of the New England Patriots). All existing investors participated, including Atlas Venture, SR One, and Partners Innovation Fund.

Pharmaceutical companies spent most of the last 10-15 years getting away from the antibiotic business largely because regulatory barriers for new drugs were high, and potential profits were low. As antibiotics continued to be fed to livestock, and overprescribed by physicians, the bugs continued to develop resistance to some otherwise quite good drugs. Public officials have increasingly dialed up the alarms in recent years as “superbugs” have emerged, and which threaten to roll back decades of progress against bacterial infections. A 2012 law called the GAIN Act, combined with some aggressive new actions at the Food and Drug Administration, however, have created more favorable conditions for startups like Spero. (Subscribers can get more depth on the antibiotic R&D revival in this Timmerman Report analysis published in March.)

Spero plans to put its new cash to work on a two-pronged strategy. One is around a series of “potentiator” molecules that it in-licensed from a research group in Finland, said CEO Ankit Mahadevia. The basic idea is that the potentiator molecules can bind with the outer envelope layer that protects many gram-negative bacteria from antibiotics that would otherwise kill them. The potentiator is supposed to essentially create an opening in that layer so that an existing antibiotic can slide through and kill the bug. “The outer layer keeps out a lot of good drugs,” Mahadevia said.

Gram-negative bacteria are among the most worrisome in medicine today because of the limited antibiotics against them. Spero believes its potentiators could clear a way for whole classes of existing antibiotics against gram-positive bacteria, like macrolides, to start working against tough gram-negative bugs as Pseudomonas aeruginosa, acinetobacter baumannii, and E. coli. Pseudomonas, in particular, is one that’s common and a troublemaker that leads to ventilator-associated pneumonia.

The other Spero program has been developed in collaboration with the pharmaceutical giant Roche. This program, building on research of Dr. Laurence Rahme at Harvard Medical School/Massachusetts General Hospital, is supposed to disarm the pathogen’s virulence—its ability make people sick by doing things like chewing up tissue around it and provoking a nasty immune reaction. The Spero drug also seeks to target a persistence mechanism in bacteria, in which the bugs develop a way to tolerate existing antibiotics. By disabling that persistence mechanism, the bug can be cleared away by the immune system, or so the thinking goes.

The potentiator program is slated to enter its first clinical trial in 2016, while the other Spero drug should be ready for that stage in 2017. Mahadevia, the founding CEO, said the company has 10 employees today and it plans to double in size in the year ahead. He plans to recruit a few experienced antibiotic developers from the Merck/Cubist layoffs. He’s not talking about nailing an experiment or two and making a quick flip to a big drugmaker, like, say, Merck. He’s talking about building a company that can get through the early phases of development, and navigate the more expensive and difficult later-stage clinical trials required for FDA approval.

“The field is ripe for someone to build a sustainable entity in the space,” Mahadevia said. “It’s such an important need for patients.”